Pulse translator for a counting apparatus



June 4, 1968 M. O'BRIEN PULSE THANSLATOR FOR A COUNTING APPARATUS 2Sheets-Sheet 1 Filed Feb. 8, 1965 QZDQBQO p s M 2 Y m \a w 3 Mm M wm n95 w 5 mg W A W% r M "6 i Q1 Q A N w qm x M x L WWWQ v Rh R 3 M: N R m lmm UK /T mm mmw h% 90 5m mQ QEZEQ IT 6 Rm mm m mwmumuu mm aw 1@ Am\ \mwhm A l 9 mm a m 1 ms Q T; fiwiiw? W y WE m Q3 (g m v i Au w a H a; i w mJune 4, 1968 M. OBRIEN 3,387,119

PULSE TRANSLATOR FOR A COUNTING APPARATUS Filed Feb. 8, 1965 2Sheets-Sheet 2 3a. 39. v v

v 1L v P- V V'\ V 36 T 3 k v v V INVENTOR MICHAEL O'BRIEN United StatesPatent 3,387,119 PULSE TRANSLATOR FOR A COUNTING APPARATUS MichaelOBrien, Grayslake, Ill., assignor to Mangood Corporation, a corporationof Illinois Filed Feb. 8, 1965, Ser. No. 431,047 9 Claims. (Cl. 235-92)ABSTRACT OF THE DISCLOSURE An electronic circuit for translating soundimpulses of extremely short duration into pulses of longer durationsufficient to operate a conventional counting apparatus. Sound impulsesare received by a microphone connected in a sensitive detecting stageand fed through an amplifying stage to trigger a monostablemultivibrator, which, in response, produces pulses of long duration byvirtue of a capacitance-resistance circuit chosen to maintain a longduration multivibrator on condition. The detecting and amplifying stagesare maintained in the triggered state during the multivibrator oncondition by regenerative circuitry. A follower stage and driver stagerespond to the multivibrator on condition to operate a conventionalcounter. A recording mechanism is periodically operated to record anaccumulated pulse count, while simultaneously shorting out theamplifying, multivibrator and follower stages.

This invention relates to counting apparatus and more particularly toelectrical counting apparatus for accurately counting very short pulses.

In trafiic counting and similar counting operations, it is desirable tocount vehicles by the sound produced in a detector tube or similardetecting member as the vehicle wheels pass over it in order to obtainrapid or high frequency count. The sound impulses produced :by passageof a vehicle wheel over a tube are of very short duration, on the orderof as short as one-half microsecond. Pulses of this duration are tooshort to operate the types of counting equipment normally employed fortraffic counting which require a counting signal on the order of thirtymilliseconds. Use of more sophisticated counters capable of respondingin a time as short as one-half microsecond would increase the costbeyond that which can be justified for traffic counting and similarcounting operations. It is accordingly one of the objects of the presentinvention to provide counting apparatus which is capable of respondingto an input signal of extremely short duration and which provides anoutput signal of much longer duration capable of operating aconventional counting device.

Another object is to provide counting apparatus in which a short inputpulse triggers a monostable multivibrator which produces output pulsesof predetermined magnitude capable of operating a counter.

According to a feature of the invention, the multivibrator maintains thepulse detecting stage and preferably the pulse amplifying stage intriggered condition during operation of the multivibrator. This Willprevent additional pulses, whether from the detecting microphone or frominternal noises in the circuit, from actually shutting off themultivibrator before it has completed its cycle, thereby to insureaccurate counting.

According to another feature of the invention, the counter includes aprinting or recording mechanism which may be periodically operated torecord the accumulated count and which functions to disable the countingcircuit during the recording operation.

The above and other objects and features of the invention will be morereadily apparent from the following description when read in connectionwith the accompanying drawings, in which:

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FIGURE 1 is a circuit diagram of counting apparatus embodying theinvention;

FIGURE 3 is a view of parts in section of a pickup tube and microphone;and

FIGURES 3a to 3k are diagrams illustrating voltage characteristics atvarious points in the circuit of FIG- URE 1.

The circuit, as shown, is adapted to receive very short pulses on theorder of one-half microsecond or more and to convert them accuratelyinto longer pulses of predetermined amplitude which are utilized foroperating a counter. The specific circuit, as shown, is particularlyadapted for traffic counting in which a sound transmitting member suchas a tube 10, shown in FIGURE 2, is stretched across or is embedded in ahighway to transmit sound waves generated by the passage of vehiclewheels across the tube. The tube is preferably connected to a hollowhousing 11 which may be of metal or any other desired material and whichis formed at one end with a tubular nipple 12 over which the tube issecured. The housing 11 contains a micro-phone 13 which may be aconventional carbon pile microphone whose resistance will change inresponse to compression of the carbon particles for a sound pulse.

As shown in FIGURE 1, the microphone 13 is connected in a circuit with acapacitor 14 across it, between a line 15 connected to the negative sideof a source of power and a line 16 which constitutes ground or thepositive side of the source of power. The source of power is preferablya battery maintaining the line 15 approximately 12 volts negativerelative to the line 16.

A potentiometer 17 is connected in series with microphone 13 and theadjustable wiper thereof is connected through a capacitor 18 to a line19. The potentiometer acts as a voltage divider to adjust thesensitivity of the circuit. The voltage at the potentiometer wiper isdesignated point A for reference to the voltage curves as will bereferred to hereinafter. The line 19 is connected to the line 15 througha resistor 21 and a rectifier 22 and to the line 16 through a similarresistor 23 and rectifier 24. A point on the line 19 between theresistors 21 and 23 is connected through a rectifier 25 to a line 26.The line 26 is connected through a capacitor 27 to the line 15 andthrough a resistor 28 to the line 16 with a point between the capacitorand resistor being connected to the rectifier 25 and also to the baseelectrode of a transistor Q1. The base of transistor Q1 is alsoconnected through a resistor 29 and line 31 to a line 32 for a purposeto appear more fully hereinafter.

The transistor Q1 has its collector connected through a resistor 33 tothe line 15, and its emitter connected through a resistor 34 to the line16. Because of the resistor 34 which acts as an emitter swamp resistorand the resistor 28 from ground to the transistor base together with theresistor 21 from the line 15 through the rectifier 25 to the transistorbase, the transistor Q1 will normally be biased to a condition in whichit is conducting but just slightly conducting. I have found that bymaintaining this transistor which constitutes the detector stage of thecircuit in a conducting condition, the detector circuit is extremelysensitive to change in voltage due to functioning of the microphone 13to increase its conductivity and to. trigger the subsequent sections ofthe circuit. The base of the transistor Q1 is designated B for purposesof illustrating the voltage conditions at that point with reference toFIG- URE 3. A point designated C between the resistor 33 and thecollector electrode of transistor Q1 is connected through a capacitor 35to a line 36 at a point therein between a rectifier 37 and a resistor 38with which a second rectifier 39 is connected in parallel. The line 36below the rectifier 37 is connected to the base of an amplifiertransistor Q2 and is also connected through a resistor 41 to a pointdesignated 1 in a line 42 for a purpose to appear later. The base oftransistor Q2 is also connected through a resistor 43 to the line 15 andthrough a capacitor 44 to the line 16. Additionally, it is connectedthrough a rectifier 45 to a line 46 for a purpose to appear hereinafter.

The collector electrode of the transistor Q2 is connected directly tothe line 16 and the emitter electrode is con nected through a resistor47 to the line 15. A point designated E between the emitter of thetransistor Q2 and the resistor 47 is connected through a capacitor 48 toa line 49. The line 49 is connected through a resistor 41 having arectifier 52 in parallel therewith to the line 15 and also through arectifier 53 to the base of a transistor Q3 constituting a portion of amonostable multivibrator stage. The base of the transistor Q3 isconnected at a point P through a resistor 54 having a capacitor 55 inparallel therewith to the line 15 and is also connected through arectifier 56 to the line 46. Additionally, it is connected through aresistor 57 and a rectifier 58 to the line 15. The collector voltage oftransistor Q3 is designated G for reference to the voltage curves ofFIGURE 3 and is connected through a resistor 59 to the line 16. Theemitter of transistor Q3 is similarly connected through a resistor 61 tothe line 15.

A point between resistor 57 and rectifier 58 is connected through acapacitor 62 to the line 42. This line is connected through a resistor63 to the line 15 and to the collector of a transistor Q4 whose emitteris connected through a resistor 64 to the line 16. The point I as shownlies between the collector of transistor Q4 and the resistor 62. Thebase of transistor Q4 whose voltage is designated H is connected througha resistor 65 and a capacitor 66 in parallel to a point in the line 32between resistor 59 and the transistor Q3.

A point in the line 42 between transistor Q4 and resistor 63 isconnected through a resistor 67 to the base of a transistor Q whichconstitutes a follower stage. The base of transistor Q5 is connectedthrough a rectifier 68 to the line 46 and the emitter is connectedthrough a resistor 69 to the line 15. The collector of transistor Q5whose voltage is designated J is connected through a resistor 71 to theline 16 with a point between the transistor and the resistor 71 beingconnected to the base of a transistor Q6 which constitutes a driverstage. The emitter of transistor Q6 is connected to line 16 through arectifier 72 and is connected to line through a resistor 73. Thecollector of transistor Q6 is connected through a rectifier 74 to theline 15 with a voltage point K between the transistor and rectifierbeing connected through a resistor 75 and a counter operating coil 76 tothe line 15.

The coil 76 is adapted to receive power pulses of predeterminedamplitude and to be energized thereby to operate a conventional counterand printer indicated generally at 77. The counter and printer 77 willstore pulses received from the coil 76 until either at predeterminedtimes or on command it will be actuated to record the stored pulses.This actuation may be from a remote point to transmit the storedinformation to the remote point but for purposes of illustration,actuation of record or printer operation is illustrated as beingcontrolled by depression of a button 78. In addition to actuating therecording operation of the counter and printer, depression of the button78 will close a switch 79 to complete a circuit from a negative voltagebias source shown as provided by connection of a switch to the line 15and the line 46 through a rectifier 81. In operation, when themicrophone 13 is in its normal unactuated condition, the transistor Q1will be conducting but the current flow therethrough will be very smalland the voltage at point C will be a relatively high negative voltage.When a sound impusle is received by the microphone, its resistance willtemporarily be decreased so that the voltage at point A will drop verysharply and will then oscillate as indicated by the curve 3A. Thisinitial strong negative voltage pulse will be transmitted throughcapacitor 18 and rectifier to the base of transistor Q1 to trigger thistransistor into conductivity. The rectifier 22 connecting one side ofthe capacitor 18 to the line 15 provides a fast recovery path for thecapacitor. The transistor Q1 will be afiected only by the first negativepulse which is a very sharp pulse as seen in FIGURE 3a on the order ofone-half microsecond and the capacitor 14 across the microphone assistsin tuning it to provide a response time on the order of one-halfmicrosecond. The capacitor 27 connected between line 15 and the base oftransistor Q1 helps to eliminate transients while the resistors 23 and28 assist in stabilizing the capacitor 18.

The transistor Q2 is normally biased to cut off as the result of itsemitter load resistor 47 and its base resistor 43 connected to the line15. Transient eifects are eliminated by the capacitor 44 While therectifiers 37 and 39 connected to the line 15 prevent premature turn-on.When the transistor Q1 is triggered to full or maximum conductivity, thevoltage at point C will raise to approximately the voltage of line 16and the capacitor 35 connected to this point will charge up from thenegative voltage of line 15 through the resistor 38 which will produce avoltage drop on the order of 8 volts. This will produce a positive pulsethrough the rectifier 37 on the base of the transistor Q2 to trigger itinto maximum conductivity. The rectifier 39 connected to the line 15provides a rapid discharge path for the capacitor 35.

With the transistor Q2 conducting, point E will have a voltagesusbtantially equal to the voltage on line 16 and will charge up thecapacitor 48 through the resistor 51 which will produce a drop ofapproximately 7 volts. This will create a positive pulse through therectifier 53 on the base of the transistor Q3 to trigger it intoconduction. The rectifiers 52 and 53 connecting the base to the negativesupply line 15 provide for fast switching time and the rectifier 52 alsoprovides a rapid discharge path for the capacitor 48.

The base of the transistor Q4 is connected to the collector electrode ofthe transistor Q3 and follows the transistor Q3. When the transistor Q3is conducting, the voltage at point G will be approximately minus 12volts due to the connection to the line 15. The capacitor 66 connectedbetween point G and the base of the transistor Q4 supplies the necessarytriggering pulses to turn on the transistor Q4. The resistor 65 willhold Q4 turned on during the time the transistor Q3 is conducting.

With transistor Q4 conducting the voltage at point I will raise toapproximately the voltage of line 16. One side of the capacitor 62 whichis connected to point I will cause the capacitor to be charged throughthe resistors 57 and 51. The capacitor 62 in conjunction with theresistors 57 and 51 and together with the combined forward currenttransfer ratios of the transistors Q3 and Q4 provide an on time forthese transistors of about 30 milliseconds which is the desired pulselength. The switching off time of this circuit which constitutes amonostable multivibrator is on the order of one-half microsecond and theswitching off time is about 1 millisecond. The rectifier 58 provides aone-half millisecond discharge path for the capacitor 62 providing arapid switching off time.

When the transistor Q3 switches on, it supplies a voltage ofapproximately minus 12 volts from line 15 through the resistor 29 to thepoint B and the base of the transistor Q1 to maintain it in conductivecondition during the full 30 millisecond period. This also provides ameans for permitting the microphone 13 to reach a steady state.Similarly, when the transistor Q4 switches on, it will supply a positivevoltage substantially equal to the voltage on line 16 through theresistor 41 to the point D and the base of the transistor Q2 to maintainit in conductive condition for the full 30 millisecond period of themonostable multivibrator allowing it to reach a steady state. Thevoltages at points B and D produced by this circuit are indicated by thevoltage graphs 3b and 3d.

The transistor Q5 functions as a monostable follower.

When the monostable circuit, including the transistor Q4 is conducting,the voltage at point I which follows the curve shown at 3i will besupplied to the base of the transistor Q5 to turn it on. When it isconductive, the voltage at point I which follows the curve shown inFIGURE 3 will be transmitted to the base of the transistor Q6 to triggerit into conduction. When this transmitter conducts it will create avoltage at the point K substantially equal to the voltage on the line 16and will cause a flow of current through the resistor 75 and the coil 76to actuate the counter.

When the counter and printer are actuated to record the accumulatedcount, either on a printed record or by transmitting it to a remotepoint, the switch 79 will be closed and will impress a negative voltageon the line 46 through the rectifier 81. This voltage will betransmitted through rectifier 45 to the base of the transistor Q2 tobias it to an 01? condition, through the rectifier 56 to the base oftransistor Q3, to bias it to non-conduction and through the rectifier 68to the base of transistor Q5 to bias it into non-conduction. Thus,during the time the recording op eration is occurring, no additionalcounts can be transmitted by the circuit thereby avoiding any possibleconfusion in operation of the circuit or the counter and printer.

While one embodiment of the invention has been shown and described indetail, it will be understood that this is illustrative only and is notto be taken as a definition of the scope of the invention, referencebeing had for this purpose to the appended claims.

What is claimed is:

1. A pulse translator for a counting apparatus comprising a microphoneto produce a variable resistance in response to a sound impulse ofextremely short duration, a circuit connected to the microphone toproduce a voltage signal in response to the sound impulse, a monostablemultivibrator circuit connected to the first named circuit and triggeredthereby to produce a voltage pulse of predetermined duration each timeit is triggered, said voltage pulse being of sufficient duration tooperate said counting apparatus.

2. A pulse translator for counting apparatus comprising in combination amicrophone to produce a variable resistance in response to a soundimpulse of extremely short duration, a circuit connected to themicrophone to produce a voltage signal in response to the sound impulse,a monostable multivibrator circuit connected to the first named circuitand triggered thereby to produce a voltage pulse of predeterminedduration each time it is triggered, said voltage pulse being ofsufiicient duration to operate said counting apparatus, and recordingmeans connected to the counting apparatus and multivibrator circuit, therecording means being operable periodically to record the pulses countedand having means to disable the multivibrator while the recording meansis actuated to record the pulses.

3. A pulse translator for a counting apparatus comprising a microphoneto produce a variable resistance in response to a sound impulse of anextremely short duration, a circuit connected to the microphone toproduce a voltage signal in response to the sound impulse, an electronicswitching device, means biasing the electronic switching device into astate of low conductivity, said circuit being connected to theelectronic switching device to bias it into a state of high conductivityin response to said voltage signal, a monostable multivibrator circuit,means responsive to current flow through the electronic switching devicewhen it is in a state of high conductivity to trigger the multivibratorcircuit, said multivibrator circuit producing a voltage pulse ofsuflicicnt duration to operate said counting apparatus.

4. The pulse translator of claim 3 in which the output of the monostablemultivibrator has regenerative circuitry feeding back to the electronicswitching device to maintain it in a high state of conductivity wheneverthe multivibrator is in an on condition.

5. The pulse translator of claim 3 in which the counting apparatusincludes recording means, means periodically to operate the recordingmeans, and means operated by the last named means to disable themultivibrator when the recording means is operated.

6. A pulse translator for a counting apparatus comprising a microphoneto produce a variable resistance in response to a sound impulse ofextremely short duration, a circuit connected to the microphone toproduce a voltage signal in response to changes in resistance of themicrophone, an electronic switching device connected to said circuit tobe triggered into high conductivity by the voltage signal, a monostablemultivibrator connected to the switching device to be triggered inresponse to current flow therethrough when it is in a high conductivitystate, the multivibrator circuit being triggered thereby to produce avoltage pulse of predetermined duration each time it is triggered, saidvoltage pulse being of sufiicient duration to operate said countingapparatus, and a connection from the multivibrator through theelectronic switching device to maintain it in a highly conductive statewhile the multivibrator is operating.

7. A pulse translator for a counting apparatus comprising a microphoneto produce a variable resistance in response to a sound impulse ofextremely short duration, a circuit connected to the microphone toproduce a voltage signal in response to changes in resistance of themicrophone, an electronic switching device connected to said circuit tobe triggered into high conductivity by the voltage signal, an amplifierconnected to the electronic switching device to produce an electricalsignal in response to current flowing through the electronic switchingdevice when it is in a state of high conductivity, a monostablemultivibrator connected to the amplifier to be triggered by theelectrical signal therefrom to produce a voltage pulse of predeterminedduration each time it is triggered, said voltage pulse being ofsufficient duration to operate said counting apparatus, and connectionsfrom the multivibrator to the electronic switching device to maintain itin a state of high conductivity and to the amplifier to maintain it inoperation.

8. The pulse translator of claim 7 including in combination, recordingmeans, means operable periodically to actuate the recording means, andmeans operable by the last made means to disable the amplifier and themultivibrator when the recording means is actuated.

9. A pulse translator in accordance with claim 7 wherein saidmultivibrator has a capacitance-resistance circuit which maintains along duration multivibrator on condition.

References Cited UNITED STATES PATENTS 3,024,414 3/1962 Nordqvist 340-38X 3,105,952 10/ 1963 Kidder 3403-8 3,319,222 5/ 1967 Grant 340-383,322,937 5/1967 OBrien 235-92 MAYNARD R. WlLBUR, Primary Examiner.

G. J. MAIER, Assistant Examiner.

